# Prior flux and background reading functionality for FLEXINVERT.jl
# Ports read_bg.f90 and related flux reading functionality

module PriorIO

using ..NetCDFIO
using ..Settings: Config, Files
using ..CoreTypes: Domain
using ..ForwardModel: FluxField, PriorFluxes, aggregate_flux_to_domain
import ..NUMERICAL_SCALE
using NCDatasets
using Dates

export read_prior_fluxes, read_background_concentrations, load_flux_field, resolve_prior_path
const SECONDS_PER_HOUR = 3600.0
const IGREG = 15 + 31 * (10 + 12 * 1582)

function fortran_julian_datetime(dt::DateTime)
    yyyy = Dates.year(dt)
    mm = Dates.month(dt)
    dd = Dates.day(dt)
    hh = Dates.hour(dt)
    mi = Dates.minute(dt)
    ss = Dates.second(dt)
    ms = Dates.millisecond(dt)

    yyyy == 0 && error("fortran_julian_datetime: year zero is undefined")
    jy = mm > 2 ? yyyy : yyyy - 1
    jm = mm > 2 ? mm + 1 : mm + 13

    julday = floor(Int, 365.25 * jy) + floor(Int, 30.6001 * jm) + dd + 1_720_995

    if dd + 31 * (mm + 12 * yyyy) >= IGREG
        ja = floor(Int, 0.01 * jy)
        julday += 2 - ja + floor(Int, 0.25 * ja)
    end

    frac_seconds = hh * 3600.0 + mi * 60.0 + ss + ms / 1_000.0
    return float(julday) + frac_seconds / 86_400.0
end

fortran_julian_datetime(dt::Date) = fortran_julian_datetime(DateTime(dt))

domain_lon_centers(domain::Domain) = [domain.rllx + (i - 0.5) * domain.rdx for i in 1:domain.nxregrid]
domain_lat_centers(domain::Domain) = [domain.rlly + (j - 0.5) * domain.rdy for j in 1:domain.nyregrid]
domain_lon_edges(domain::Domain) = collect(domain.rllx:domain.rdx:(domain.rllx + domain.rdx * domain.nxregrid))
domain_lat_edges(domain::Domain) = collect(domain.rlly:domain.rdy:(domain.rlly + domain.rdy * domain.nyregrid))

function regrid_flux_to_domain(flux::FluxField, domain::Domain)
    if size(flux.data, 1) == domain.nxregrid && size(flux.data, 2) == domain.nyregrid
        return flux
    end

    lon_edges = domain_lon_edges(domain)
    lat_edges = domain_lat_edges(domain)
    aggregated = zeros(Float64, domain.nxregrid, domain.nyregrid, size(flux.data, 3))

    for t in 1:size(flux.data, 3)
        slice = flux.data[:, :, t]
        aggregated[:, :, t] .= aggregate_flux_to_domain(slice, flux.lon, flux.lat, lon_edges, lat_edges)
    end

    new_lon = domain_lon_centers(domain)
    new_lat = domain_lat_centers(domain)

    return FluxField(flux.name, aggregated, new_lon, new_lat, flux.time,
                     flux.units, flux.scaling_factor, flux.time_units)
end

"""
    read_prior_fluxes(files::Files, cfg::Config, domain::Domain) -> PriorFluxes

Read all prior flux fields (NEE, fossil fuel, ocean) from NetCDF files.

# Arguments
- `files`: File paths configuration
- `cfg`: Configuration settings
- `domain`: Domain information for spatial/temporal bounds

# Returns
- PriorFluxes structure with loaded flux fields
"""
function read_prior_fluxes(files::Files, cfg::Config, domain::Domain)
    @info "Reading prior flux fields"

    # Read NEE fluxes (nested and global)
    nee_nested = nothing
    if !isempty(files.filenest_nee)
        try
            path = resolve_prior_path(files, files.filenest_nee, cfg.datei)
            nee_nested = load_flux_field(path, "NEE",
                                         isempty(files.varnest_nee) ? files.varname_nee : files.varnest_nee,
                                         isempty(files.lonnest_nee) ? files.lonname_nee : files.lonnest_nee,
                                         isempty(files.latnest_nee) ? files.latname_nee : files.latnest_nee,
                                         isempty(files.timenest_nee) ? files.timename_nee : files.timenest_nee,
                                         get(Dict(:coeff_ff => cfg.coeff_ff), :coeff_nee, 1.0);
                                         cfg=cfg, domain=domain)
            nee_nested = regrid_flux_to_domain(nee_nested, domain)
            @info "Loaded nested NEE flux field: $(size(nee_nested.data))"
        catch e
            @warn "Could not load nested NEE flux field: $e"
        end
    end

    nee_global = nothing
    if !isempty(files.filename_nee)
        try
            path = resolve_prior_path(files, files.filename_nee, cfg.datei)
            nee_global = load_flux_field(path, "NEE",
                                         files.varname_nee,
                                         files.lonname_nee,
                                         files.latname_nee,
                                         files.timename_nee,
                                         get(Dict(:coeff_ff => cfg.coeff_ff), :coeff_nee, 1.0);
                                         cfg=cfg, domain=domain)
            nee_global = regrid_flux_to_domain(nee_global, domain)
            @info "Loaded global NEE flux field: $(size(nee_global.data))"
        catch e
            @warn "Could not load global NEE flux field: $e"
        end
    end

    nee_flux = nee_nested !== nothing ? nee_nested : nee_global

    # Read fossil fuel fluxes
    ff_nested = nothing
    if !isempty(files.filenest_ff)
        try
            path = resolve_prior_path(files, files.filenest_ff, cfg.datei)
            ff_nested = load_flux_field(path, "fossil_fuel",
                                        isempty(files.varnest_ff) ? files.varname_ff : files.varnest_ff,
                                        isempty(files.lonnest_ff) ? files.lonname_ff : files.lonnest_ff,
                                        isempty(files.latnest_ff) ? files.latname_ff : files.latnest_ff,
                                        isempty(files.timenest_ff) ? files.timename_ff : files.timenest_ff,
                                        cfg.coeff_ff_reg; cfg=cfg, domain=domain)
            ff_nested = regrid_flux_to_domain(ff_nested, domain)
            @info "Loaded nested fossil fuel flux field: $(size(ff_nested.data))"
        catch e
            @warn "Could not load nested fossil fuel flux field: $e"
        end
    end

    ff_global = nothing
    if !isempty(files.filename_ff)
        try
            path = resolve_prior_path(files, files.filename_ff, cfg.datei)
            ff_global = load_flux_field(path, "fossil_fuel",
                                        files.varname_ff,
                                        files.lonname_ff,
                                        files.latname_ff,
                                        files.timename_ff,
                                        cfg.coeff_ff; cfg=cfg, domain=domain)
            ff_global = regrid_flux_to_domain(ff_global, domain)
            @info "Loaded global fossil fuel flux field: $(size(ff_global.data))"
        catch e
            @warn "Could not load global fossil fuel flux field: $e"
        end
    end

    ff_flux = ff_nested !== nothing ? ff_nested : ff_global

    # Read ocean fluxes
    ocean_nested = nothing
    if !isempty(files.filenest_ocn)
        try
            path = resolve_prior_path(files, files.filenest_ocn, cfg.datei)
            ocean_nested = load_flux_field(path, "ocean",
                                           isempty(files.varnest_ocn) ? files.varname_ocn : files.varnest_ocn,
                                           isempty(files.lonnest_ocn) ? files.lonname_ocn : files.lonnest_ocn,
                                           isempty(files.latnest_ocn) ? files.latname_ocn : files.latnest_ocn,
                                           isempty(files.timenest_ocn) ? files.timename_ocn : files.timenest_ocn,
                                           1.0; cfg=cfg, domain=domain)
            ocean_nested = regrid_flux_to_domain(ocean_nested, domain)
            @info "Loaded nested ocean flux field: $(size(ocean_nested.data))"
        catch e
            @warn "Could not load nested ocean flux field: $e"
        end
    end

    ocean_global = nothing
    if !isempty(files.filename_ocn)
        try
            path = resolve_prior_path(files, files.filename_ocn, cfg.datei)
            ocean_global = load_flux_field(path, "ocean",
                                           files.varname_ocn,
                                           files.lonname_ocn,
                                           files.latname_ocn,
                                           files.timename_ocn,
                                           1.0; cfg=cfg, domain=domain)
            ocean_global = regrid_flux_to_domain(ocean_global, domain)
            @info "Loaded global ocean flux field: $(size(ocean_global.data))"
        catch e
            @warn "Could not load global ocean flux field: $e"
        end
    end

    ocean_flux = ocean_nested !== nothing ? ocean_nested : ocean_global

    # Read background concentrations
    background = read_background_concentrations(files, cfg)

    return PriorFluxes(nee_flux, ff_flux, ocean_flux, background,
                       nee_global, ff_global, ocean_global)
end

"""
    resolve_prior_path(files::Files, filename_pattern::String, datei::Int) -> String

Resolve file path for prior data using path_prior and filename patterns.
Replaces YYYY and YYYYMM tokens with actual dates.

# Arguments
- `files`: Files configuration
- `filename_pattern`: Filename pattern with YYYY/YYYYMM tokens
- `datei`: Start date in YYYYMMDD format

# Returns
- Resolved full file path
"""
function resolve_prior_path(files::Files, filename_pattern::String, datei::Int)
    # Extract year and month from datei
    yyyy = datei ÷ 10000
    yyyymm = datei ÷ 100

    # Replace tokens in filename
    resolved_filename = replace(filename_pattern, "YYYYMM" => string(yyyymm))
    resolved_filename = replace(resolved_filename, "YYYY" => string(yyyy))

    # Combine with path_prior
    resolved_path = joinpath(files.path_prior, resolved_filename)

    @info "Resolved prior path: $filename_pattern -> $resolved_path"
    return resolved_path
end

"""
    load_flux_field(file_path::String, flux_name::String, var_name::String,
                   lon_name::String, lat_name::String, time_name::String,
                   scaling_factor::Float64=1.0) -> FluxField

Load a single flux field from a NetCDF file using explicit variable names.

# Arguments
- `file_path`: Path to NetCDF file
- `flux_name`: Name/type of flux for identification
- `var_name`: Variable name in NetCDF file
- `lon_name`: Longitude coordinate variable name
- `lat_name`: Latitude coordinate variable name
- `time_name`: Time coordinate variable name
- `scaling_factor`: Multiplicative scaling factor to apply

# Returns
- FluxField structure with loaded data
"""
function load_flux_field(file_path::String, flux_name::String, var_name::String,
                        lon_name::String, lat_name::String, time_name::String,
                        scaling_factor::Float64=1.0;
                        cfg::Union{Config,Nothing}=nothing,
                        domain::Union{Domain,Nothing}=nothing)
    if !isfile(file_path)
        error("Flux file not found: $file_path")
    end

    @info "Loading flux field '$flux_name' from: $file_path"

    try
        Dataset(file_path, "r") do ds
            # Use specified variable name or fall back to common names
            flux_var = nothing
            flux_data = nothing

            if !isempty(var_name) && haskey(ds, var_name)
                flux_var = ds[var_name]
                flux_data = Array(flux_var)
                @info "Found flux variable: $var_name"
            else
                # Fallback to common variable names for fluxes
                flux_var_names = ["flux", "nee", "fossil", "ocean", "co2_flux", "emissions"]
                for fallback_name in flux_var_names
                    if haskey(ds, fallback_name)
                        flux_var = ds[fallback_name]
                        flux_data = Array(flux_var)
                        @info "Found flux variable (fallback): $fallback_name"
                        break
                    end
                end
            end

            if flux_data === nothing
                # List available variables for debugging
                available_vars = [k for k in keys(ds)]
                error("No flux variable found in $file_path. Available variables: $available_vars")
            end

            # Read coordinate variables using specified names or fallbacks
            lon = nothing
            lat = nothing
            time = nothing

            # Longitude
            lon_attr_name = nothing
            for lon_candidate in [lon_name, "lon", "longitude", "x"]
                if haskey(ds, lon_candidate)
                    lon_attr_name = lon_candidate
                    lon = Array(ds[lon_candidate])
                    break
                end
            end
            if lon === nothing
                error("No longitude coordinate found in $file_path")
            end

            # Latitude
            lat_attr_name = nothing
            for lat_candidate in [lat_name, "lat", "latitude", "y"]
                if haskey(ds, lat_candidate)
                    lat_attr_name = lat_candidate
                    lat = Array(ds[lat_candidate])
                    break
                end
            end
            if lat === nothing
                error("No latitude coordinate found in $file_path")
            end

            # Time
            raw_time = nothing
            time_units = nothing
            time_var = nothing
            for time_candidate in [time_name, "time", "t"]
                if haskey(ds, time_candidate)
                    time_var = ds[time_candidate]
                    raw_time = Array(time_var)
                    for attr_name in ("units", "unit")
                        if haskey(time_var.attrib, attr_name)
                            time_units = String(time_var.attrib[attr_name])
                            break
                        end
                    end
                    break
                end
            end

            time = convert_time_axis(raw_time, time_units)
            if time === nothing
                time = [0.0]
                if ndims(flux_data) == 2
                    flux_data = reshape(flux_data, size(flux_data)..., 1)
                end
            end

            lon_indices = nothing
            lat_indices = nothing
            if domain !== nothing
                if domain.nxregrid > 0
                    lon_indices = domain_slice_indices(
                        lon,
                        domain.rllx,
                        domain.nxregrid,
                        domain.rdx;
                        label="longitude"
                    )
                end
                if domain.nyregrid > 0
                    lat_indices = domain_slice_indices(
                        lat,
                        domain.rlly,
                        domain.nyregrid,
                        domain.rdy;
                        label="latitude"
                    )
                end
                if lon_indices !== nothing
                    lon = lon[lon_indices]
                end
                if lat_indices !== nothing
                    lat = lat[lat_indices]
                end
            end

            # Determine dimension ordering for efficient slicing
            dim_names = dimnames(flux_var)
            selectors = Any[Colon() for _ in dim_names]
            lon_dim = nothing
            lat_dim = nothing
            for (i, name) in enumerate(dim_names)
                if name == lon_attr_name
                    lon_dim = i
                    if lon_indices !== nothing
                        selectors[i] = lon_indices
                    end
                elseif name == lat_attr_name
                    lat_dim = i
                    if lat_indices !== nothing
                        selectors[i] = lat_indices
                    end
                end
            end

            flux_data = Array(@view flux_var[selectors...])

            # Ensure flux data is ordered as (lon, lat, time)
            lon_len = length(lon)
            lat_len = length(lat)
            time_len = length(time)
            flux_data = orient_flux_data(flux_data, lon_len, lat_len, time_len)

            # Get units
            units = "kg/m²/s"  # Default units
            for attr_name in ("units", "unit")
                if haskey(flux_var.attrib, attr_name)
                    units = String(flux_var.attrib[attr_name])
                    break
                end
            end

            unit_scale = flux_unit_scale(units, cfg)

            # Match the Fortran ingestion path: flux slices are scaled by NUMSCALE
            # during loading so that the subsequent footprint division yields
            # physical units.
            effective_scaling = scaling_factor * unit_scale * NUMERICAL_SCALE
            return FluxField(flux_name, flux_data, lon, lat, time, units,
                             effective_scaling, time_units)
        end
    catch e
        error("Error reading flux file $file_path: $e")
    end
end

"""
    read_background_concentrations(files::Files, cfg::Config) -> Vector{Float64}

Read background/prior concentration values.

# Arguments
- `files`: File paths configuration
- `cfg`: Configuration settings

# Returns
- Vector of background concentrations (single value or per-observation)
"""
function read_background_concentrations(files::Files, cfg::Config)
    # Check if background concentration file is specified (file_bg is the actual field)
    if !isempty(files.file_bg)
        try
            return read_background_file(files.file_bg)
        catch e
            @warn "Could not read background file: $e"
        end
    end

    # Default fallback aligns with Fortran behaviour: missing files imply zero background
    default_bg = 0.0  # ppm
    @info "Using fallback background concentration: $default_bg ppm (no background file specified)"
    return [default_bg]
end

"""
    read_background_file(file_path::String) -> Vector{Float64}

Read background concentrations from a file (NetCDF or text).

# Arguments
- `file_path`: Path to background concentration file

# Returns
- Vector of background concentration values
"""
function read_background_file(file_path::String)
    if !isfile(file_path)
        error("Background file not found: $file_path")
    end

    file_ext = lowercase(splitext(file_path)[2])

    if file_ext == ".nc"
        # Read from NetCDF
        Dataset(file_path, "r") do ds
            # Try common variable names for background concentrations
            bg_var_names = ["background", "bg", "conc", "concentration", "mixing_ratio"]

            for var_name in bg_var_names
                if haskey(ds, var_name)
                    bg_data = Array(ds[var_name])
                    @info "Read background concentrations from NetCDF variable: $var_name"
                    return vec(bg_data)  # Flatten to 1D vector
                end
            end

            error("No background concentration variable found in $file_path")
        end
    else
        # Read from text file
        @info "Reading background concentrations from text file: $file_path"
        data = Float64[]

        open(file_path, "r") do io
            for line in eachline(io)
                line = strip(line)
                if !isempty(line) && !startswith(line, "#")
                    try
                        push!(data, parse(Float64, line))
                    catch e
                        @warn "Could not parse line '$line' as float: $e"
                    end
                end
            end
        end

        if isempty(data)
            error("No valid background concentration data found in $file_path")
        end

        @info "Read $(length(data)) background concentration values"
        return data
    end
end


function normalize_time_axis(raw_time)
    if raw_time === nothing
        return nothing
    end

    if raw_time isa AbstractVector{<:Real}
        return Float64.(raw_time)
    elseif raw_time isa AbstractVector{<:Dates.AbstractDateTime}
        return Float64.(fortran_julian_datetime.(raw_time))
    elseif raw_time isa AbstractVector{<:Dates.AbstractDate}
        return Float64.(fortran_julian_datetime.(Dates.DateTime.(raw_time)))
    else
        try
            return Float64.(raw_time)
        catch
            return Float64.(collect(raw_time))
        end
    end
end

function convert_time_axis(raw_time, time_units)
    normalized = normalize_time_axis(raw_time)
    if normalized === nothing || time_units === nothing
        return normalized
    end

    if raw_time isa AbstractVector{<:Dates.AbstractDateTime} || raw_time isa AbstractVector{<:Dates.AbstractDate}
        return normalized
    end

    units_lower = lowercase(strip(time_units))
    if !occursin("since", units_lower)
        return normalized
    end

    parts = split(units_lower, "since")
    unit_str = strip(parts[1])  # e.g., "days"
    origin_str = strip(parts[2])

    base_dt = parse_time_origin(origin_str)
    base_julian = fortran_julian_datetime(base_dt)

    factor = unit_to_day_multiplier(unit_str)
    return base_julian .+ normalized .* factor
end

function flux_unit_scale(units::AbstractString, cfg::Union{Config,Nothing})
    scale = 1.0
    units_lower = lowercase(strip(String(units)))

    if cfg !== nothing
        if occursin("micromol", units_lower) || occursin("µmol", units_lower) || occursin("umol", units_lower)
            scale *= cfg.molarmass * 1e-9
        elseif occursin("mol", units_lower)
            scale *= cfg.molarmass * 1e-3
        elseif occursin("kg", units_lower)
            scale *= 1.0
        elseif occursin("g", units_lower)
            scale *= 1e-3
        end
    end

    if occursin("h-1", units_lower) || occursin("per hour", units_lower) || occursin("/h", units_lower)
        scale /= SECONDS_PER_HOUR
    end

    return scale
end

function parse_time_origin(origin_str::AbstractString)
    cleaned = replace(String(origin_str), "T" => " ")
    formats = (
        dateformat"yyyy-mm-dd HH:MM:SS",
        dateformat"yyyy-mm-dd HH:MM",
        dateformat"yyyy-mm-dd"
    )

    for fmt in formats
        try
            return DateTime(cleaned, fmt)
        catch
        end
    end

    error("Unable to parse time origin '$origin_str'")
end

function unit_to_day_multiplier(unit_str::AbstractString)
    str = lowercase(String(unit_str))
    if startswith(str, "day")
        return 1.0
    elseif startswith(str, "hour")
        return 1.0 / 24.0
    elseif startswith(str, "minute")
        return 1.0 / 1440.0
    elseif startswith(str, "second")
        return 1.0 / 86400.0
    else
        @warn "Unrecognized time unit '$unit_str', assuming days"
        return 1.0
    end
end

function orient_flux_data(data::Array, lon_len::Int, lat_len::Int, time_len::Int)
    nd = ndims(data)
    if nd == 3
        sz = size(data)
        if sz[1] == lon_len && sz[2] == lat_len && sz[3] == time_len
            return data
        elseif sz[3] == lon_len && sz[2] == lat_len && sz[1] == time_len
            return permutedims(data, (3, 2, 1))
        elseif sz[2] == lon_len && sz[1] == lat_len && sz[3] == time_len
            return permutedims(data, (2, 1, 3))
        else
            @warn "Unexpected flux data dimensions $(sz); attempting heuristic reordering"
            return permutedims(data, (3, 2, 1))
        end
    elseif nd == 2
        data_perm = permutedims(data, (2, 1))
        return reshape(data_perm, size(data_perm,1), size(data_perm,2), 1)
    else
        return data
    end
end

function infer_coordinate_step(coord::Vector{Float64})
    n = length(coord)
    if n <= 1
        return 0.0
    end

    diffs = diff(coord)
    for Δ in diffs
        if abs(Δ) > eps(Float64)
            return Δ
        end
    end

    return 0.0
end

function adjust_start_edge(edge::Float64, candidate_edges::Vector{Float64})
    # Attempt to match periodic longitude grids by shifting start edge by multiples of 360°.
    if isempty(candidate_edges)
        return edge
    end

    span = maximum(candidate_edges) - minimum(candidate_edges)
    if span < 350.0
        return edge
    end

    shifts = (-720.0, -360.0, 0.0, 360.0, 720.0)
    best_edge = edge
    best_gap = Inf
    for shift in shifts
        shifted = edge + shift
        gap = minimum(abs.(candidate_edges .- shifted))
        if gap < best_gap
            best_gap = gap
            best_edge = shifted
        end
    end
    return best_edge
end

function domain_slice_indices(coord::Vector{Float64}, start_edge::Float64, cell_count::Int,
                              expected_spacing::Float64; label::AbstractString="coordinate")
    cell_count <= 0 && return nothing
    isempty(coord) && return nothing

    step = infer_coordinate_step(coord)
    if abs(step) <= eps(Float64)
        step = expected_spacing
    end

    if abs(step) <= eps(Float64)
        error("Cannot determine grid spacing for $label axis (all coordinate differences are zero)")
    end

    half_step = step / 2.0
    edges = coord .- half_step
    effective_edge = adjust_start_edge(start_edge, edges)

    # Identify the first cell whose western/southern edge aligns with the requested start edge.
    _, idx = findmin(abs.(edges .- effective_edge))
    start_value = edges[idx]
    tolerance = max(abs(step), abs(expected_spacing), 1.0) * 1.0e-6
    if abs(start_value - effective_edge) > tolerance
        error("Flux file does not provide the expected $label start edge $(effective_edge); closest edge is $(start_value)")
    end

    last_idx = idx + cell_count - 1
    if last_idx > length(coord)
        error("Flux file does not cover the requested $label window starting at $(effective_edge) with $cell_count cells")
    end

    return idx:last_idx
end

function subset_indices(coord::Vector{Float64}, low_edge::Float64, high_edge::Float64)
    n = length(coord)
    n == 0 && return nothing

    lo = min(low_edge, high_edge)
    hi = max(low_edge, high_edge)

    step = n > 1 ? abs(coord[2] - coord[1]) : 0.0

    lower_bound = lo - 1e-6
    upper_bound = hi + 1e-6

    if step > 0
        lower_bound = lo + 0.5 * step - 1e-6
        upper_bound = hi - 0.5 * step + 1e-6
        if lower_bound > upper_bound
            lower_bound, upper_bound = upper_bound, lower_bound
        end
    end

    start_idx = findfirst(x -> x >= lower_bound, coord)
    stop_idx = findlast(x -> x <= upper_bound, coord)

    if start_idx === nothing || stop_idx === nothing
        return 1:n
    end

    if start_idx > stop_idx
        start_idx, stop_idx = stop_idx, start_idx
    end

    return start_idx:stop_idx
end


"""
    interpolate_flux_to_grid(flux::FluxField, target_lon::Vector, target_lat::Vector,
                           target_time::Vector) -> Array{Float64, 3}

Interpolate flux field to target grid and time coordinates.

# Arguments
- `flux`: Source flux field
- `target_lon`: Target longitude coordinates
- `target_lat`: Target latitude coordinates
- `target_time`: Target time coordinates

# Returns
- Interpolated flux data on target grid
"""
function interpolate_flux_to_grid(flux::FluxField, target_lon::Vector, target_lat::Vector,
                                target_time::Vector)
    # This is a placeholder for spatial/temporal interpolation
    # A full implementation would use proper interpolation methods

    @info "Interpolating $(flux.name) flux to target grid (placeholder implementation)"

    # For now, return zeros with correct dimensions
    return zeros(Float64, length(target_lon), length(target_lat), length(target_time))
end

end # module PriorIO
